For the purpose of protecting the connections, etc. of optical fiber cables, a cable protection case for wrapping them for protection is generally used. For example, the cable protection case is built up of a combination of halves obtained by splitting an elongate cylindrical case longitudinally. After the connections, etc. of optical fiber cables are received in that combination, the cylindrical case is assembled with the splitting surfaces of the halves in a butt-to-butt relation. Thereafter, the splitting surfaces are firmly fixed against taking apart.
Both end faces of such a cable protection case are required to remain closed up with the cables inserted through it for the purpose of preventing entrance of liquids from outside.
So far, both ends faces of such a cable protection case have generally been closed up by the following method.
There are end face-sealing members at the ready that are attachable to the end faces to provide sealing of both end faces of the cable protection case. The end face-sealing member is available in two types: one type having a cable insertion inlet opening larger than the outer diameter of an actually inserted cable, wherein a packing or bushing working as a spacer or a rubber tape of certain thickness is wrapped around a gap between the cable insertion inlet and the cable thereby making sure sealing of the gap between the cable insertion inlet and the cable, and another type using a sealing tape for making sure air tightness or liquid tightness in addition to the above arrangement.
Besides, there is yet another type of the end face-sealing member having a tapered hole inside, in which case a given position of the tapered portion is cut on the ground in such a way as to be compatible with the outer diameter of the cable used.
In the above method using the packing or bushing as the spacer, however, there is typically the need for always having several spacers at the ready and storing them in hand in such a way as to be compatible with several cable outer diameters, resulting in a problem that a parts count gets too increased for satisfactory handling.
The wrapping method using the rubber tape or sealing tape to make sure sealing capability, on the other hand, is difficult to work with, and removal of these tapes puts too much burden on the addition and maintenance of cables in particular.
With the end face-sealing member having a tapered hole inside, it would be difficult to determine the position of cutting because which portion is to be cut to obtain a given inner diameter is invisible to the naked eye.
To solve these problems, Patent Publication 1 (U.S. Pat. No. 5,048,382), cited here as a pertinent prior art, shows a method for producing a rubber elastic sealing device having a plurality of concentric rings. The rubber elastic sealing device produced by such a method includes a plurality of removable concentric ring-form slit portions, and an associated removable ring-form slit portion is optionally taken out of the site of the desired ring diameter depending on the outer diameter of the cable inserted, thereby having the desired hole diameter size.
In the method, as set forth in Patent Publication 1, of producing a rubber elastic sealing device having a plurality of concentric rings, however, the rubber to be processed has a durometer A hardness of 35 to 75. Such rubber hardness is too high to ensure sufficient sealing capability as an end face-sealing member for cables.
When the rubber hardness is lower than described above in terms of durometer A hardness of less than 30 as an example, a problem with the method set forth in Patent Publication 1 is to be unable to provide stable formation of removable concentric rings.